With evolution and a microminiaturization of microprocessor engineering and electronics, the need for high-capacitance tantalum capacitors has rapidly increased. Qualifying demands on tantalum powder for use in electrolytic capacitors on purity and developed surface of powder particles are very high and can not always be achieved by known means of powder metallurgy.
There are well-known methods of processing high purity metal powders using vacuum-arc, plasma and electron beam heating of initial metals. Similarly, the known subsequent centrifugal atomization of a melt and cooling to form grain-like or flake-like metal particles have many merits, such as refining the microstructure, giving homogeneous distribution of many parameters, and forming an amorphous phase. However, these methods are inconvenient in view of the high melting point of tantalum. In particular, the collision of the melted particles with a cooled metal surface (usually the copper) results in contaminating the refractory drops with the constituents of the impacted metal surface.
One conventional production method of a tantalum powder for anodes of electrolytic capacitors includes mechanical milling tantalum ingots. The resulting powder has the porous structure similar to agglomerated powder and fits the requirements of developed surface, but does not meet the requirements of surface contamination, which substantially impairs parameters of capacitors. Thus, what is needed is an improved method and apparatus for plasma processing of tantalum particles.